COMPUTATIONAL STUDY OF TRANSITION

OF OIL-WATER FLOW MORPHOLOGY

DUE TO SUDDEN CONTRACTION IN

MICROFLUIDIC CHANNEL

JOYDIP CHAUDHURI

DEPARTMENT OF CHEMICAL ENGINEERING

IIT GUWAHATI

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

PRESENTATION PLAN

Introduction

Application of microfluidics

Motivation of the work

Summary of the work

Use of COMSOL Multiphysics

Mathematical formulation

Results and discussion

Conclusion

Future scopes

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INTRODUCTION

MICROFLUIDICS

MICRO

Small sub millimeter scale

Small size

Low energy

Effects of micro domain

FLUIDICS

Behavior, precise control and manipulation of fluids

Dealing with the fluid flow

Low Reynolds number flow

Small diameter

Low velocity

Laminar flowNo traditional

mixing like turbulent flow

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APPLICATIONS OF MICROFLUIDICS

Microfluidics

Electronic

Biological

Lab on a chip devices

Reaction Engineering

3

The origins and the

future of

microfluidics

George M.

Whitesides,

Nature 442, 368-373,

2006

Parallel screening of

an in situ "click"

chemistry library in

integrated

microfluidics Hsian-

Rong Tseng, UCLA

Fluid thread

breakup under

microfluidic

confinement with

applications in oil

recovery and

biology, João T.

Cabral, Polymers

& Microfluidics

Group, Imperial

College, London

Bio pixel

microfluidic

bacteria chip,

http://www.extre

metech.com/extr

eme/111617-

glowing-bacteria-

biopixels-the-

sensor-displays-

of-the-future

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

MOTIVATION OF THE WORK

Achieve droplet driven flow from any type of flow pattern

Study the effects of interfacial tension of the two phases (oil and

water) and the contraction/orifice diameter

Tuning of the droplet diameter by changing the orifice position and

the diameter

Droplet formation in an economic way i.e. without using any

external force fields

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APPLICATION OF COMSOL MULTIPHYSICS

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GEOMETRY

Selection of appropriate coordinate

Determining of the domain shape and size

Simplifications, if possible

do = orifice diameter

d = micro channel diameter

Y

X

do = 100 μm-200 μm

d = 500 μm

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MESH

6770 – 6924 number of mesh elements

Physics controlled mesh

Triangular mesh

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PHYSICS

Flow conditions:- Viscous fluids- Laminar flow- Incompressible flow- Irrotational flow

Fluid properties:- Constant density- Constant viscosity- Newtonian fluids- Immiscible fluids

Flow models:- Multi phase flow- Two phase flow, Phase field

Inlets: Normal inflow velocity

Outlet: Pressure with

no viscous stress

Wall: No slip, Impermeable

Contact angle: 140˚

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GOVERNING EQUATIONS

Conservation of Mass – Continuity equation:

Navier-Stokes Equation:

where, and

0t

u

0 u

1 20.5 1 1

1 20.5 1 1

Incompressible flow

Ti i i i

τ u u st G f

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RESULTS

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FLOW PARAMETER VALUES

Viscosity:- Oil: 0.01 Pa s

- Water: 0.001 Pa s

Density:- Oil: 1000 kg/m3

- Water: 1000 kg/m3

Velocity:- Oil: 0.1 m/s

- Water: 0.01 m/s

Interfacial Tension (γ):

- Varied from 0.0258 to 0.04 N/m

Contact angle (θ) :

- Equilibrium contact angle of a water droplet on the wall and embedded

inside oil is set to 140°

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Increased frequency

of dropletsHigher pressure drop

at the contraction

Water squeezes at the

orifice

CHANGE IN FLOW MORPHOLOGY

Change in flow

structures

Contraction / Orifice

Abrupt velocity

difference of Oil and

WaterSmaller droplets

12

Water

Oil

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

EFFECT OF ORIFICE DIAMETER

(a)

(b)

(c)

(d)

ho

hd

0 0.4 0.8 1.20

0.2

0.4

0.6

0.8

1

= 0.0258 N/m = 0.03 N/m

= 0.04 N/m

(e)

Image (e) shows the variation of dimensionless droplet diameter with

dimensionless orifice diameter upon changing the interfacial tension

From images (a), (b),

(c) and (d) we can say

Droplet diameter

decreased

Orifice diameter

decreased

hd = dd/dDimensionless droplet

diameter

dd = droplet diameter

ho = do/d Dimensionless orifice

diameter

do= orifice diameter 13Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

(c)

(b)

(d)

(a)

ho

hd

0 0.4 0.8 1.20.2

0.4

0.6

0.8

1

= 0.0258 N/m

= 0.03 N/m

= 0.04 N/m

(e)

From this combined image it is also evident that the droplet

diameter also depends on the position of the contraction

From images (a), (b),

(c) and (d) we can say

Droplet diameter

decreased

Orifice diameter

decreased

Shifting of contraction from

T-junction towards right

Droplet diameter increased

Droplet frequency decreased

EFFECT OF ORIFICE POSITION

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CONCLUSIONS

Controlled oil-water flow patterns by using a contraction near a T-

junction microchannel

Smaller diameter orifice can facilitate smaller sized flow structures

Frequency and size of droplets can be controlled by the size of

orifices and also by their positions

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FUTURE SCOPES

Effect in flow patterns by adding two or more contractions in the

downstream of the T-junction

Effect in flow patterns by adding orifice at the inlets

Effect in flow structures by switching the inlets between oil and

water

Study the flow morphology by varying different other parameters

like velocity ratio

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REFERENCES

S. W. Li, J. H. Xu , J. Tan , Y. J. Wang , G. S. Luo Controllable Preparation of Monodisperse O/W and W/O

Emulsions in the Same Microfluidic Device, Langmuir, 22, 7943 (2006).

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Engineering Science, 66, 1463 (2011).

X. Z. Lin, A. D. Terepka, and H. Yang, Synthesis of Silver Nanoparticles in a Continuous Flow Tubular

Microreactor, Nano Letters, 4, 2227 (2004).

J. Skommer, J. Akagi, K. Takeda, Y. Fujimura, K. Khoshmanesh, and D. Wlodkowic, Multiparameter lab-on-a-chip

flow cytometry of the cell cycle, Biosensors and Bioelectronics, 42, 586 (2013).

V. Kumar, M. Paraschivoiu, and K. D. P. Nigam, Single-phase fluid flow and mixing in microchannels, Chemical

Engineering Science, 66, 1329 (2011).

A. Sharma, V. Tiwari, V. Kumar, T. K. Mandal, D. Bandyopadhyay, Localized Electric Field Induced Transition and

Miniaturization of Two-Phase Flow Patterns inside Microchannels, Electrophoresis, 35, 2930–2937 (2014).

A. Kawahara, P. M. Y. Chung, and M. Kawaji, Investigation of two-phase flow pattern, void fraction and pressure

drop in a microchannel, International Journal of Multiphase Flow, 28, 1411 (2002).

P. M. Y. Chung and M. Kawaji, The effect of channel diameter on adiabatic two-phase flow characteristics in

microchannels, International Journal of Multiphase Flow, 30, 735 (2004).

H. Foroughi and M. Kawaji, Viscous oil–water flows in a microchannel initially saturated with oil: flow patterns and

pressure drop characteristics, International Journal of Multiphase Flow, 37, 1147 (2011).

T. Cubaud, B. M. Jose, S. Darvishi, and R. Sun, Droplet breakup and viscosity-stratified flows in microchannels,

International Journal of Multiphase Flow, 39, 29 (2012).17Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

ACKNOWLEDGEMENT

Project Supervisors

- Dr. Dipankar Bandyopadhyay

- Dr. Tapas Kumar Mandal

Mr. Seim Timung

My Labmates

Department of Chemical Engineering, IIT Guwahati

Centre for Nanotechnology, IIT Guwahati

Department of Science and Technology, Govt. of India

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Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore